import time
from itertools import permutations
from typing import Callable, Tuple

import numpy.typing as npt

from common import plot_plan, read_data


def exhaustive_search(distances: npt.NDArray) -> Tuple[float, Tuple]:
    """An implementation of exhaustive search.

        This implementation takes a permutation iterator, then maps each
        element to a tuple containing the travel distance of that permutation
        and the permutation tuple itself. Finally the function returns the
        tuple that contains the smallest travel distance.

    Args:
        distances (npt.NDArray): An array containing distances to travel.

    Returns:
        A tuple containing the shortest travel distance and its corresponding
        permutation.
    """

    size = len(distances)

    return min(  # Find the smallest travel distance from the array
        map(  # Map the permutation array to contain tuples (distance, permutation)
            lambda perm: (
                sum([distances[perm[i - 1], perm[i]] for i in range(size)]),
                perm,
            ),
            permutations(range(size)),
        ),
    )


if __name__ == "__main__":
    cities, data = read_data("./european_cities.csv")

    # A loop timing finding the optimal solution for different n
    for n in range(6, 11):
        # Time exhaustive search
        t0 = time.time_ns()
        distance, perm = exhaustive_search(data[:n, :n])
        t1 = time.time_ns()

        time_elapsed_ms = (t1 - t0) / 1_000_000.0

        print(f"Exhaustive search for the {n} first cities:")
        print(f"distance             : {distance:>12.6f}km")
        print(f"time to find solution: {time_elapsed_ms:>12.6f}ms\n")


""" Running example

oblig1 on  main [?] via 🐍 v3.12.6 took 7s
❯ python exhaustive_search.py
Exhaustive search for the 6 first cities:
distance             :  5018.810000km
time to find solution:     1.105330ms

Exhaustive search for the 7 first cities:
distance             :  5487.890000km
time to find solution:    10.089604ms

Exhaustive search for the 8 first cities:
distance             :  6667.490000km
time to find solution:    78.810508ms

Exhaustive search for the 9 first cities:
distance             :  6678.550000km
time to find solution:   765.676230ms

Exhaustive search for the 10 first cities:
distance             :  7486.310000km
time to find solution:  8281.795515ms
"""